The accommodation of freight on freight carriers, such as aircraft, requires a reliable power driven conveyor system for moving the freight between stored and unstored conditions. In addition to reliability, the conveyor system must be as light weight as possible, and the conveyor system must be as powerful as possible.
With respect to the weight of the conveyor system, it will be readily appreciated that the more cargo which can be loaded on an aircraft, the greater the profit to the carrier. In aircraft cargo shipping in particular, weight capacities of the aircraft must be strictly observed. Once the weight capacity of the aircraft has been reached, no more freight will be loaded into the aircraft even through there is frequently vacant additional space remaining in the cargo area. If the aircraft could be made lighter, e.g., by reducing the weight of the conveyor system, then more freight could be loaded into the vacant additional space in the cargo area. Therefore, a reduction in the weight in the freight conveyor system will allow additional freight to be loaded into the aircraft, and therefore return greater profits to the shipper.
With respect to the power requirements of the conveyor system, as weight is trimmed from various portions of the aircraft, including the conveyor system, the weight of the freight stored in the aircraft may become heavier. Alternatively, on aircraft dedicated or dedicatable to the shipping of cargo, the main deck is available to receive cargo containers which are substantially larger and heavier than containers received into the lower deck cargo area. The heavier the freight moved by the conveyor system, the nearer the individual power drive unit assemblies become taxed to overload. To remedy this problem, the prior art teaches to increase the size, and hence the weight, of the driving motor in the power drive unit assembly. Or, as an alternative, the prior art teaches that more power drive unit assemblies may be used at closer spaced intervals to move the heavier cargo. However, as the size and number, and consequently the weight, of each power drive unit assembly increases, the lighter the total weight of freight which may be received into the cargo area in order to prevent an overload of the aircraft weight capacity.
Therefore, the prior art is deficient and in need of a power drive unit assembly which is both light weight and powerful, while requiring very small space within the aircraft.